Process to prevent scale adhesion using condensation product of a diamino heterocyclic and a quinone

ABSTRACT

A process to prevent the adhesion of polymer scale during the polymerization of vinyl monomers which involves coating the internal reactor surfaces with the condensation product of a diamino heterocyclic and an amine compound. The coating is applied as an alkaline solution followed by drying. The coating is effective in preventing scale adhesion on the portions of the reactor exposed to the liquid phase reaction medium as well as the gas-liquid interface. The polymer resulting from use of the coating exhibits few fish eyes and little discoloration.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a polymer scale preventive agent for use in polymrization of a monomer having an ethylenically unsaturated double bond, a polymerization vessel effective in preventing polymer scale deposition, and a process for producing a polymer using the same.

2. Description of the Prior Art

Heretofore, methods for polymerization of a monomer having an ethylenically unsaturated double bond have been known, such as suspension, emulsion, solution, gas phase and bulk polymerization processes and the like. In any of these polymerization processes, polymer scale is liable to be deposited on the areas with which the monomer comes into contact, such as inner walls, stirring equipment and so on of a polymerization vessel.

The deposition of the polymer scale results in, disadvantages that the yield of the polymer and cooling capacity of the polymerization vessel are lowered, and that the polymer scale may peel off and mix into a polymeric product, thereby impairing the quality of formed products obtained by processing the polymeric product. In addition, removal of deposited polymer scale is very laborious and time-consuming. Further, the polymer scale contains unreacted monomers and, therefore, may cause physical disorders in the operators, which has been a very serious problem in recent years.

For preventing polymer scale deposition on the polymerization vessel inner wall and so forth, methods have been known, for example, a method in which a polymer scale preventive agent comprising a polar organic compound such as amine compounds, quinone compounds, aldehyde compounds, etc. is applied to the polymerization vessel inner wall and so on to form a coating and a method in which such compounds are added to an aqueous medium (Japanese Patent Publication (KOKOKU) No. 45-30343 (1970)), as practiced in some instances of suspension polymerization of vinyl chloride.

However, these methods have the disadvantage that, although the polymer scale preventive effect is exhibited while polymerization is repeated for up to about 5 or 6 batches, the effect diminishes if the number of repeated batches of polymerization exceeds 5 or 6 (that is, the scale preventive effect is poor in durability). The disadvantage is emphasized particularly where a watersoluble catalyst is used for polymerization, and, in this point, the polymer scale prevention according to these methods is unsatisfactory industrially.

For overcoming the above disadvantage, Japanese Pre-examination Patent Publication (KOKAI) No. 53-13689 (1978) proposes a method in which the inner wall, etc. of a polymerization vessel are coated with a polymer scale preventive agent comprising a condensation product of an aromatic amine compound as an effective constituent. Where the polymer scale preventive agent is applied to the areas with which monomers come into contact, such as the inner wall surface of a polymerization vessel, and a coating is thereby formed, it is possible to repeat about 100 to 200 batches of polymerization without causing deposition of polymer scale on the areas located in the liquid-phase region inside the polymerization vessel. Besides, even in the above-mentioned case where a water-soluble catalyst is used, deposition of polymer scale in the liquid-phase region is similarly prevented.

However, after the coating of the polymer scale preventive agent comprising a condensation product of an aromatic amine compound as its effective constituent is formed, there still remains a drawback that polymer scale deposition may occur on the areas around the interface between the liquid phase and the gas phase located at an upper portion of the interior of the polymerization vessel.

Once polymer scale deposition occurs on the areas around the interface between the gas and liquid phases, the deposited scale will grow gradually as polymerization runs are repeated, and at last it may peel off to be incorporated into the polymeric product. If the polymeric product with the polymer scale thus mixed therein is processed into formed products such as sheets or the like, the polymer scale causes generation of many fish eyes in the formed products, thereby lowering seriously the quality of the formed products.

Besides, the polymeric product obtained upon polymerization is required to have a high whiteness. That is, when a polymeric product is formed into a sheet or the like without any addition of a coloring agent, the resulting formed product is more or less colored and such coloration, called initial coloration, is desired to be as slight as possible. However, the aforesaid coating of the polymer scale preventive agent which contains a condensation product of an aromatic amine compound may peel off or dissolve in the polymerization mass, to be incorporated into the polymeric product; in such a case, the resulting formed products will have a lowered whiteness, i.e., a higher initial coloration.

SUMMARY OF THE INVENTION

Accordingly it is an object of the present invention to provide a polymer scale preventive agent for use in polymerization of a monomer having an ethylenically unsaturated double bond that can prevent effectively the deposition of polymer scale, not only on the areas in the liquid-phase region but also on the areas around the interface between the gas and liquid phases inside a polymerization vessel, and that makes it possible to produce a polymer having a very small number of fish eyes and slight initial coloration when processed into formed products such as sheets or the like; and a polymerization vessel and a process for producing a polymer which utilize the polymer scale preventive agent.

The present invention provides, as a means of achieving the above object, a polymer scale preventive agent for use in polymerization of a monomer having an ethylenically unsaturated double bond, comprising an alkaline solution containing a condensation product of:

(A) a heterocyclic compound having at least two amino groups, and

(B) a quinone compound.

The present invention also provides a polymerization vessel for polymerizing a monomer having an ethylenically unsaturated double bond, comprising a coating on its inner wall surfaces, wherein said coating has been formed by applying an alkaline solution containing a condensation product of

(A) a heterocyclic compound having at least two amino groups, and

(B) a quinone compound, followed by drying.

Further, the present invention provides a process for producing a polymer of a monomer having an ethylenically unsaturated double bond, which comprises polymerizing the monomer in a polymerization vessel having a coating on its inner wall surfaces, whereby polymer scale is prevented from being deposited, wherein said coating has been formed by applying an alkaline solution containing a condensation product of

(A) a heterocyclic compound having at least two amino groups, and

(B) a quinone compound, followed by drying.

According to the present invention, deposition of polymer scale in a polymerization vessel can be effectively prevented, not only on the areas in the liquid-phase region but also on the areas around the interface between the gas phase and the liquid phase.

Therefore, where polymerization is conducted by applying the present invention, the operation of removing polymer scale need not be performed every run of polymerization, and productivity is thereby improved.

In addition, the polymer obtained by application of the present invention can be processed into formed products such as sheets or the like which have very few fish eyes.

Furthermore, the formed products have good quality in regard of initial coloration. More specifically, the formed products have a luminosity index (L value) in the Hunter's color difference equation described in JIS Z 8730 (1980) of, for example, 70 or more in the case of vinyl chloride polymers and 80 or more in the case of SBR.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Component (A)

The component (A) is a heterocyclic compound having at least two amino groups (--NH₂).

The heterocyclic compound having at least two amino groups (--NH₂) includes, for example, the compounds having the following general formula (1):

    (R.sup.1).sub.k X(NH.sub.2).sub.2                          ( 1)

wherein R¹ is --OH, --COOH, --SO₃ H, --NH₂, --Cl, --Br, --I, --SH, --NO₂, --COCH₃, --OCH₃, --N(CH₃)₂, --C₆ H₅ or an alkyl group having 1 to 3 carbon atoms, and where a plurality of R¹ groups are present, they may be the same or different from each other, k is an integer of 0 to 9, and X is a heterocyclic group with a valence of k+2.

The heterocyclic group represented by X herein refers to a group which has at least one heterocycle in its molecule. The heterocycle may be condensed with a carbon homocycle and/or another heterocycle. The heterocyclic group includes, for example, those which are each derived from a heterocyclic compound such as pyrrole, indole, isoindole, carbazole, porphyrin, oxazole, thiazole, benzothiazole, imidazole, pyrazole, triazole, thiadiazole, pyridine, pyrimidine, quinoline, acridine, phenanthridine, phenanthroline, naphthyridine, furan, benzofuran, pyran, pyrrone, benzopyrylium, cumarin and xanthone, by removal of k+2 hydrogen atoms attached to a ring of said compound.

Specific examples of the heterocyclic compound having at least two amino groups include the followings:

Pyrrole compounds such as 2,4-diaminopyrrole, 2,5-diaminopyrrole and the like;

Indole compounds such as 2,5-diaminoindole, 3,5-diaminoindole and the like;

Isoindole compounds such as 1,3-diaminoisoindole, 4,7-diaminoisoindole and the like;

Carbazole compounds such as 2,6-diaminocarbazole, 3,6-diaminocarbazole and the like;

Oxazole compounds such as 2,4-diaminooxazole, 4-acetyl-2,5-diaminooxazole and the like;

Thiazole compounds such as 2,4-diaminothiazole, 2,4-diamino-5-methylthiazole, 2,4-diamino-5-phenylthiazole, 2,4-diaminothiazole-5-carboxylic acid, 2,4-diaminothiazole-5-sulfonic acid and the like;

Benzothiazole compounds such as 2,4- and 2,5-diaminobenzothiazoles, 2,4-diaminobenzothiazole-6-carboxylic acid, 2,4-diaminobenzothiazole-6-sulfonic acid and the like;

Imidazole compounds such as 2,4-diaminoimidazole, 2,5-diaminoimidazole and the like;

Pyrazole compounds such as 3,4-diaminopyrazole, 3,5-diaminopyrazole and the like;

Thiadiazole compounds such as 2,5-diamino-1,3,4-thiadiazole and the like;

Pyridine compounds such as 2,3-, 2,5-, 2,6- and 3,4-diaminopyridine, 4-hydroxy-2,6-diaminopyridine, 4-chloro-2,6-diaminopyridine and the like;

Pyrimidine compounds such as 2,4-, 2,6- and 4,6-diaminopyrimidine, 2,4,5-triaminopyrimidine, 4,5,6-triaminopyrimidine, 2,4-diamino-6-hydroxypyrimidine, 4,6-diamino-2-hydroxypyrimidine, 2,6-diamino-4-hydroxypyrimidine, 2,4-diaminopyrimidine-5-carboxylic acid, 2,4-diaminopyrimidine-6-carboxylic acid, 4,6-diaminopyrimidine-2-carboxylic acid, 2,6-diaminopyrimidine-4-carboxylic acid, 4,6-diaminopyrimidine-2-sulfonic acid, 2,6-diaminopyrimidine-4-sulfonic acid, 2,4-diaminopyrimidine-6-sulfonic acid, 2,4,5-triamino-6-hydroxypyrimidine, 2,4-diamino-6-mercaptopyrimidine, 4,6-diamino-2-mercaptopyrimidine and the like;

Quinoline compounds such as 2,3-, 2,4-, 3,4-, 4,6-, 4,8-, 5,6-, 5,7-, 5,8-, 6,8- and 7,8-diaminoquinolines, 5,8-diamino-6-methoxyquinoline, 5,8-diaminoquinoline-2-carboxylic acid, 5,8-diaminoquinoline-2-sulfonic acid, 5,8-diamino-6-hydroxyquinoline and the like;

Acridine compounds such as 1,6-, 1,7-, 1,9-, 2,4-, 2,5-, 2,6-, 2,7-, 2,9-, 3,5-, 3,6-, 3,8-, 3,9- and 4,9-diaminoacridines, 4,9-diamino-2-hydroxyacridine, 4,9-diaminoacridine-2-carboxylic acid, 4,9-diaminoacridine-2-sulfonic acid and the like;

Phenanthridine compounds such as 3,6-diaminophenanthridine, 6,9-diaminophenanthridine and the like;

Phenanthroline compounds such as 2,4-diamino-1,10-phenanthroline, 2,9-diamino-1,10-phenanthroline and the like;

Naphthyridine compounds such as 2,6-diamino-1,5-naphthyridine, 2,4-diamino-1,8-naphthyridine and the like;

Furan compounds such as 2,4-diaminofuran, 2,5-diaminofuran and the like;

Benzofuran compounds such as 3,6-diaminobenzofuran, 4,6-diaminobenzofuran and the like;

Pyran compounds such as 2,6-diaminopyran, 3,6-diaminopyran and the like;

Pyrrone compounds such as 3,6-diamino-α-pyrrone, 2,6-diamino-γ-pyrrone and the like;

Benzopyrylium compounds such as 2,7-diamino-4-benzopyrylium chloride, 4,7-diamino-2-benzopyrylium chloride and the like;

Cumarin compounds such as 3,4-diaminocumarin, 5,7-diaminocumarin and the like; and

Xanthone compounds such as 1,6-diaminoxanthone, 2,7-diaminoxanthone and the like.

Among the components (A) above, preferred are pyridine compounds, acridine compounds, pyrimidine compounds, thiazole compounds and quinoline compounds which each have at least two amino groups.

Among the above components (A), particularly preferred are 2,6-diaminopyridine, 3,6-diaminoacridine, 1,6-diaminoacridine, 3,9-diaminoacridine, 4,9-diamino-2-hydroxyacridine, 4,9-diaminoacridine-2-sulfonic acid, 2,4-diamino-6-hydroxypyrimidine, 4,6-diaminopyrimidine, 2,4,5-triaminopyrimidine, 2,4-diaminopyrimidine-5-carboxylic acid, 4,6-diaminopyrimidine-2-sulfonic acid, 2,4-diaminothiazole, 2,4-diaminothiazole-5-carboxylic acid, 5,8-diaminoquinoline and 4,8-diaminoquinoline.

These components (A) may be used either singly or in combination of two or more.

Component (B)

The component (B) is a quinone compound, which includes, for example:

the benzoquinone compounds of the following general formulas (2) and (3): ##STR1## wherein in the formulas (2) and (3), (R²)'s may be the same or different and each are --H, --NH₂, --Cl, --Br, --OH, --NO₂, --OCH₃, --OCH₃, --N(CH₃)₂, --COOH, --SO₃ H or an alkyl group having 1 to 3 carbon atoms; and

the naphthoquinone compounds of the following general formulas (4) and (5): ##STR2## wherein in the formulas (4) and (5), (R²)'s may be the same or different and each are as defined above, and (R³)'s may be the same or different and each are --H, --Cl, --Br, --OH, --OCH₃, --OCH₃, --CH₃, --COOH or --SO₃ H.

The benzoquinone compounds of the above general formulas (2) and (3) include, for example, o- and p-benzoquinones, hydroxy-p-benzoquinone, chloro-p-benzoquinone, bromo-p-benzoquinone, duroquinone, chloranil and the like.

The naphthoquinone compounds of the above general formulas (4) and (5) include, for example, 6-methyl-1,4-naphthoquinone, 2-methyl-1,4-naphthoquinone, lawsone, juglone, plumbagin, α-naphthoquinone, β-naphthoquinone and the like.

Among the components (B) above, preferred are o- and p-benzoquinone, α-naphthoquinone, β-naphthoquinone and lawsone.

The aforementioned quinone compounds may be used either singly or in combination of two or more.

Condensation reaction

The condensation product of the components (A) and (B), which is the indispensable constituent of the polymer scale preventive agent according to the present invention, can be prepared by reacting the components (A) and (B) with each other in a suitable solvent, optionally in the presence of a catalyst as required, normally at a temperature of room temperature to 200° C. for 0.5 to 100 hours, and preferably at room temperature to 150° C. for 3 to 30 hours.

Since the component (B) acts also as a condensation catalyst, it is normally unnecessary to add other condensation catalyst to the reaction system. However, other condensation catalysts than the component (B) may be added, as required. The other condensation catalysts which can be added include, for example, elemental or molecular simple-substance halogens such as iodine, bromine, chlorine, fluorine and the like; oxo-acids and oxo-acid salts of halogen, such as iodic acid, periodic acid, potassium periodide, sodium perchlorate and the like; inorganic peroxides such as hydrogen peroxide, sodium peroxide, potassium persulfate, ammonium persulfate and the like; organic peroxides such as peracetic acid, benzoyl peroxide, cumene hydroperoxide, perbenzoic acid, p-menthane hydroperoxide and the like; chlorides and sulfates of a metal selected from the group consisting of iron and copper, such as ferrous chloride, ferric chloride, copper sulfate, cuprous chloride and the like; azo compounds such as α,α'-azobisisobutyronitrile, α,α'-azobis-2,4-dimethylvaleronitrile and the like; aromatic nitro compounds such as o-, m- and p-oxynitrobenzenes, o-, m- and p-nitroanisoles, o-, m- and p-chloronitrobenzenes, o-, m- and p-nitrobenzoic acids, o-, m- and p-nitrobenzenesulfonic acids, and the like; and so forth.

As a solvent for carrying out the above condensation reaction, organic solvents such as alcohols, ketones, esters and the like can be used, among which preferred are those organic solvents which are miscible with water. Preferable examples of the organic solvents miscible with water include alcohols such as methanol, ethanol, propanol and the like, ketones such as acetone, methyl ethyl ketone and the like, and esters such as methyl acetate, ethyl acetate and the like, among which particularly preferred are alcohols. Further, mixed solvents of water and such an organic solvent miscible with water as above-mentioned may also be used.

The medium for condensation reaction normally has a pH of 1 to 13, and pH adjusters may be used without any particular restrictions.

The relative amounts of the components (A) and (B) to be brought into the condensation reaction depend on the kinds of the compounds (A) and (B) and solvent used, reaction temperature, reaction time and so on. Normally, it is preferable to use the component (B) in an amount of 0.01 to 10 parts by weight, more preferably from 0.1 to 5 parts by weight, per part by weight of the component (A). If the amount of the component (B) is too large or too small, the resulting condensation product has a lower effect in preventing polymer scale deposition.

Polymer scale preventive agent comprising an alkaline solution containing the components (A) and (B)

The polymer scale preventive agent according to the present invention comprises an alkaline solution containing the condensation product of the above-described components (A) and (B). The polymer scale preventive agent is applied to inner wall surfaces, etc. of a polymerization vessel and is dried to form a coating, whereby polymer scale can be prevented from being deposited on the polymerization vessel inner wall or the like.

To prepare the polymer scale preventive agent, the solution containing the condensation product obtained by the condensation reaction as above is admixed with a solvent (which will be described below) as required, and the pH of the resulting solution is controlled to the alkaline side. Alternatively, the polymer scale preventive agent may be prepared by putting the condensation product-containing solution into cold water to precipitate the condensation product, then separating the precipitate by filtration and drying it, adding the solvent (described below) to the dried precipitate, and controlling the pH of the resulting solution to the alkaline side.

Because the polymer scale preventive agent of the present invention is made alkaline, the solubility of the condensation product of the components (A) and (B) in the solvent is improved and a uniform solution can be obtained. Therefore, by applying the polymer scale preventive agent to the polymerization vessel inner wall surfaces, etc., an improved scale preventive effect can be obtained. The pH of the inventive polymer scale preventive agent preferably ranges from 7.5 to 13.5, more preferably from 8.0 to 13.5. For pH adjustment, alkaline compounds can be used, for example, alkali metal compounds such as LiOH, NaOH, KOH, Na₂ CO₃, Na₂ HPO₄ and the like, ammonium compounds such as NH₄ OH and the like, organic amine compounds such as ethylenediamine, monoethanolamine, diethanolamine, triethanolamine, and so forth.

The solvent for use in preparation of the polymer scale preventive agent of the present invention includes, for example, water; alcohol solvents such as methanol, ethanol, propanol, butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 3-methyl-1-butanol, 2-methyl-2-butanol, 2-pentanol and the like; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and the like; ester solvents such as methyl formate, ethyl formate, methyl acetate, ethyl acetate, methyl acetoacetate and the like; ether solvents such as 4-methyldioxolan, ethylene glycol diethyl ether and the like; furans; aprotic solvents such as dimethylformamide, dimethyl sulfoxide, acetonitrile and the like; and so forth. These may be used either singly or as a mixed solvent of two or more thereof on a case-by-case basis.

Among the above solvents, preferred are water land mixed solvents of water and an organic solvent miscible with water. The organic solvents miscible with water include, for example, alcohol solvents such as methanol, ethanol, propanol and the like; ketone solvents such as acetone, methyl ethyl ketone and the like; and ester solvents such as methyl acetate, ethyl acetate and the like. The mixed solvents of water and an organic solvent miscible with water preferably contain the organic solvent in such an amount that there is no fear about inflammation, explosion or the like and safety in handling is ensured as to virulence, etc. Specifically, the amount of the organic solvent is preferably not more than 50% by weight, a more preferable amount being not more than 30% by weight.

Other ingredients

In order to further enhance the polymer scale preventive effect, it is preferable to add to the above-described agent at least one member selected from the group consisting of (C) a water-soluble polymeric compound, (D) an inorganic colloid and (E) an alkali metal silicate.

These additives (C) to (E) enhance the scale preventive effect, presumably by interacting with the condensation product in such a manner as to improve the hydrophilicity of the surfaces being coated (in the case of the water-soluble polymeric compound (C)) or to improve adhesion to the polymerization vessel wall and so on (in the cases of the inorganic colloid (D) and the alkali metal silicate (E)).

(C) Water-soluble polymeric compound

The water-soluble polymeric compounds (C) which can be added to the polymer scale preventive agent include, for example, nonionic polymeric compounds such as gelatin, casein and the like; anionic polymeric compounds such as polyacrylic acid, polystyrenesulfonic acid, carboxymethyl cellulose, alginic acid, and the like; cationic nitrogen-containing polymeric compounds such as polyvinyl pyrrolidone, polyacrylamide and the like; hydroxyl group-containing polymeric compounds such as polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, pectin and the like; and so forth.

Among the water-soluble polymeric compounds above-mentioned, preferred are gelatin, casein, polyacrylic acid, carboxymethyl cellulose, polyvinyl pyrrolidone and pectin.

The water-soluble polymeric compounds (C) may be used either singly or in combination of two or more.

The component (C) is added in an amount of normally 1 to 1000 parts by weight, preferably 5 to 200 parts by weight, per 100 parts by weight of the condensation product (A).

(D) Inorganic colloid

The inorganic colloids (D) which can be added to the polymer scale preventive agent are those obtained by a condensing method or a dispersing method using water as a dispersion medium, with the colloidal particles ranging from 1 to 500 μm in size.

Specifically, the applicable inorganic colloids include, for example, colloids of an oxide, a hydroxide or a mixture thereof, the oxide and hydroxide being those of a metal such as aluminum, thorium, titanium, zirconium, antimony, tin, iron and the like; colloids of tungstic acid, vanadium pentoxide, gold and silver; silver iodide sol; colloids of selenium, sulfur, silica and the like; and so forth.

Among the inorganic colloids above, preferred are colloids of an oxide, a hydroxide or a mixture thereof, the oxide and hydroxide being those of a metal selected from the group consisting of aluminum, titanium, zirconium, tin and iron; and colloidal silica.

The inorganic colloids (D) are added in an amount of normally 1 to 1000 parts by weight, preferably 5 to 500 parts by weight, per 100 parts by weight of the condensation product (A).

(E) Alkali metal silicates

The alkali metal silicates (E) which can be added to the polymer scale preventive agent of the present invention include, for example, metasilicates (M₂ SiO₃), orthosilicates (M₄ SiO₄), disilicates (M₂ Si₂ O₃), trisilicates (M₃ Si₃ O₇), sesquisilicates (M₄ Si₃ O₁₀) and the like of alkali metals such as lithium, sodium, potassium and the like (wherein M stands for an alkali metal such as lithium, sodium and potassium); and water glass.

The alkali metal silicates (E) may be used either singly or in combination of two or more.

The component (E) is added in an amount of normally 1 to 1000 parts by weight, preferably 5 to 500 parts by weight, per 100 parts by weight of the component (A).

Where the component (D) and the component (E) are used in combination, the total amount of the components (D) and (E) is preferably 1 to 1000 parts by weight, more preferably 5 to 500 parts by weight, per 100 parts by weight of the component (A).

For best improving the polymer scale preventing effect, it is preferable to use a combination of the water-soluble polymeric compound (C) with the inorganic colloid (D) or a combination of the water-soluble polymeric compound (C) with the alkali metal silicate (E). Where the components (C) and (D) are used in combination, the amount of the component (D) is preferably 5 to 3000 parts by weight, more preferably 50 to 1000 parts by weight, per 100 parts by weight of the component (C). Where the components (C) and (E) are used in combination, the component (E) is preferably used in an amount of 5 to 3000 parts by weight, more preferably 50 to 1000 parts by weight, per 100 parts by weight of the component (C).

The concentration of the condensation product of the components (A) and (B) in the coating liquid is not particularly limited, as long as the total coating weight described later can be obtained. Normally, the concentration of the condensation product is on the order of 0.001 to 5% by weight, a preferable concentration being on the order of 0.01 to 1% by weight. Where the components (C) to (E) are added, the total concentration of the condensation product and these components (C) to (E) is preferably on the order of 0.1 to 20% by weight, more preferably on the order of 0.2 to 6% by weight.

Formation of coating

To form a coating on inner wall surfaces of a polymerization vessel using the polymer scale preventive agent prepared as above-described, first the agent is applied to the inner wall surfaces of the polymerization vessel. Then, the applied agent is dried sufficiently at a temperature ranging, for example, from room temperature to 100° C., optionally followed by washing with water.

The polymer scale preventive agent is preferably applied to not only the inner wall surfaces of a polymerization vessel but also other areas with which the monomer comes into contact during polymerization, for example, stirring blades, stirring shaft, baffles, condensers, headers, search coil, bolts, nuts, etc.

More preferably, for formation of the coating, the polymer scale preventive agent is applied to areas with which the monomer does not come into contact during polymerization but on which polymer scale may be deposited, for example, the inner surfaces, etc. of equipment and pipes of an unreacted monomer recovery system. Specifically, such areas include the inner surfaces of monomer distillation columns, condensers, monomer stock tanks, valves, and so on.

The method of applying the polymer scale preventive agent to the inner wall surfaces of a polymerization vessel is not particularly restricted, and includes, for example, brush coating, spray coating, a method by filling the polymerization vessel with the polymer scale preventive agent followed by withdrawal thereof, and the automatic coating methods as disclosed in Japanese Pre-examination Patent Publication (KOKAI) Nos. 57-61001 (1982) and 55-36288 (1980), Japanese Patent Publication (KOHYO) Nos. 56-501116 (1981) and 56-501117 (1981), and Japanese Pre-examination Patent Publication (KOKAI) No. 59-11303 (1984), etc.

The method of drying wet coated surfaces provided by application of the polymer scale preventive agent, is not restricted, either. For example, the following methods can be used: a method in which, after the agent is applied, hot air with a suitable elevated temperature is blown to the coated surface; a method in which the inner wall surfaces of a polymerization vessel and the surfaces of other parts to be coated are preliminarily heated, for example, to a temperature of 30° to 80° C., and the polymer scale preventive agent is directly applied to the heated surfaces; and so on. After dried, the coated surfaces are washed with water if necessary.

The coating obtained in this manner has a total coating weight after dried of normally 0.001 to 5 g/m², preferably 0.05 to 2 g/m².

The formed coating has good durability and retains the polymer scale-preventing action; therefore, the above-described coating operation may not necessarily be carried out every batch of polymerization. Accordingly, productivity is improved.

Polymerization

After the formation of the coating on the inner wall surfaces of a polymerization vessel, and preferably also on other areas with which monomer may come into contact during polymerization, etc. by the coating operation as above, polymerization is carried out in accordance with conventional procedures. That is, a monomer having an ethylenically unsaturated double bond, a polymerization initiator (catalyst), and optionally a polymerization medium such as water, etc., a dispersing agent such as suspending agents, solid dispersing agents, nonionic or anionic emulsifying agents, etc., and the like are charged into the polymerization vessel, and then polymerization is carried out according to conventional procedures.

The monomers having an ethylenically unsaturated double bond which can be polymerized by applying the process of the present invention include, for example, vinyl halides such as vinyl chloride and the like; vinyl esters such as vinyl acetate, vinyl propionate and the like; acrylic acid, methacrylic acid, and their esters and salts; maleic acid, fumaric acid, and their esters and anhydrides; diene monomers such as butadiene, chloroprene, isoprene and the like; styrene; acrylonitrile; vinylidene halides; vinyl ethers; and so forth. These monomers may be used either singly or in combination of two or more.

There are no particular restrictions on the type of polymerization to which the process according to the present invention can be applied. That is, the process of the present invention is effective in any of such polymerization types as suspension polymerization, emulsion polymerization, solution polymerization, bulk polymerization, and gas phase polymerization. Particularly, the process of the present invention is more suited to polymerizations in an aqueous medium, such as suspension polymerization and emulsion polymerization.

In the following, taking the cases of suspension polymerization and emulsion polymerization as an example, general procedures of polymerization will be described.

First, water and a dispersing agent are charged into a polymerization vessel. Subsequently, thee polymerization vessel is evacuated to reduce the internal pressure to a value of 0.1 to 760 mmHg, and a monomer is then charged (whereupon the internal pressure usually takes a value of 0.5 to 30 kgf/cm².G). A polymerization initiator is charged into the vessel before and/or after charging the monomer. Subsequently, polymerization is carried out at a reaction temperature of 30° to 150° C. During the polymerization, one or more of water, a dispersing agent and a polymerization initiator may be added, if necessary. Reaction temperature during the polymerization is different depending on the kind of monomer to be polymerized. For example, in the case of polymerizing vinyl chloride, polymerization is carried out at 30° to 80° C.; in the case of polymerizing styrene, polymerization is carried out at 50° to 150° C. The polymerization may be judged to be completed when the pressure inside the polymerization vessel has fallen to a value of 0 to 7 kgf/cm².G or when cooling water which is let flow into and out of a jacket provided around the polymerization vessel has come to show approximately equal inlet and outlet temperatures (i.e., when liberation of heat due to polymerization reaction has subsided). The amounts of the water, dispersing agent and polymerization initiator to be charged for polymerization are 20 to 500 parts by weight, 0.01 to 30 parts by weight, and 0.01 to 5 parts by weight, respectively, per 100 parts by weight of the monomer.

In solution polymerization, an organic solvent such as toluene, xylene, pyridine, etc. is used as the polymerization medium, in place of water. A dispersing agent may be used, if necessary. The other conditions for polymerization are generally the same as those described for suspension and emulsion polymerizations.

In bulk polymerization, after a polymerization vessel is evacuated to a pressure of about 0.01 mmHg to about 760 mmHg, a monomer and a polymerization initiator are charged into the polymerization vessel, and then polymerization is carried out at a reaction temperature of -10° C. to 250° C. For example, the reaction temperature is 30° to 80° C. for polymerization of vinyl chloride, and is 50° to 150° C. for polymerization of styrene.

Where polymerization is carried out by applying the process of the present invention, it is possible to prevent polymer scale from being deposited, regardless of the materials of the inner wall, etc. of a polymerization vessel. For example, where the polymerization vessel is made of a stainless steel or other steel as well as where the polymerization vessel is a glass-lined one or the like, the polymer scale deposition can be prevented from occurring during polymerization.

Those additive materials which are conventionally added in polymerization systems can be used without any limitations. That is to say, the process of the present invention can effectively prevent polymer scale deposition in polymerization systems which may contain additive materials including, for example, polymerization initiators such as t-butyl peroxyneodecanoate, bis(2-ethylhexyl) peroxydicarbonate, 3,5,5-trimethylhexanoyl peroxide, α-cumyl peroxyneodecanoate, cumene hydroperoxide, cyclohexanone peroxide, t-butyl peroxypivalate, bis(2-ethoxyethyl) peroxydicarbonate, benzoyl peroxide, lauroyl peroxide, 2,4-dichlorobenzoyl peroxide, diisopropyl peroxydicarbonate, α,α'-azobisisobutyronitrile, α,α'-azobis-2,4-dimethylvaleronitrile, potassium peroxodisulfate, ammonium peroxodisulfate, p-menthane hydroperoxide, etc.; suspending agents comprised of, for example, natural or synthetic polymeric compounds such as partially saponified polyvinyl alcohols, polyacrylic acids, vinyl acetatemaleic anhydride copolymers, cellulose derivatives (e.g. hydroxypropyl methyl cellulose), gelatin, etc.; solid dispersing agents such as calcium phosphate, hydroxyapatite, etc.; nonionic emulsifying agents such as sorbitan monolaurate, sorbitan trioleate, polyoxyethylene alkyl ether, etc.; anionic emulsifying agents such as sodium lauryl sulfate, sodium alkylbenzenesulfonates (e.g. sodium dodecylbenzenesulfonate), sodium dioctylsulfosuccinate, etc.; fillers such as calcium carbonate, titanium oxide, etc.; stabilizers such as tribasic lead sulfate, calcium stearate, dibutylin dilaurate, dioctyltin mercaptide, etc.; lubricants such as rice wax, stearic acid, cetyl alcohol, etc.; plasticizers such as DOP, DBP, etc.; chain transfer agents such as mercaptans (e.g. t-dodecyl mercaptan), trichloroethylene, etc.; pH adjusters, and so forth.

In addition to being used for formation of the coating on the inner wall surfaces, etc. of the polymerization vessel, the polymer scale preventive agent of the present invention may further be added directly to the polymerization system, whereby a further enhanced effect in preventing deposition of polymer scale can be obtained. In that case, the addition amount of the agent suitably ranges from about 10 to about 1000 ppm based on the total weight of the monomer or monomers charged into the polymerization vessel. At the time of adding the polymer scale preventive agent, care should be taken not to affect adversely the fish eye, bulk specific gravity, particle size distribution or other qualities of the resulting polymeric product.

EXAMPLES

The present invention will now be described in detail below, with reference to working examples thereof and comparative examples. In the tables below, the experiments bearing a No. marked with * are comparative examples, and the other experiments, bearing a non-marked No., are working examples of the present invention.

Preparation Example 1 Preparation of condensation product No. 1

A 2-liter reaction vessel equipped with a reflux condenser was charged with 900 g of methanol and 40 g of 2,6-diaminopyridine as component (A), followed by stirring at room temperature to dissolve 2,6-diaminopyridine in methanol.

To the methanol solution thus obtained, 60 g of α-naphthoquinone was added as component (B). After heating to 65° C., the reactants in the vessel were reacted at 65° C. for 10 hours. After the reaction was over, the reaction system was cooled to give a methanol solution of a condensation product, which is hereinafter referred to as condensation product No. 1.

Preparation of condensation product Nos. 2 to 26

Condensation products were prepared in the same manner as in the above preparation of the condensation product No. 1 except for using the component (A) (heterocyclic compound having at least two amino groups) and component (B) (quinone compound) given in Table 1 and the solvent shown in Table 2. Total concentration of (A)+(B), weight ratio of (A):(B), reaction temperature and reaction time are also set forth in Table 2.

                  TABLE 1                                                          ______________________________________                                         Condensation                                                                   product                                                                        No.      (A)               (B)                                                 ______________________________________                                          1       2,6-Diaminopyridine                                                                              α-Naphthoquinone                               2*      2,6-Diaminopyridine                                                                              α-Naphthoquinone                               3*      2,6-Diaminopyridine                                                                              --                                                   4       2,6-Diaminopyridine                                                                              p-Benzoquinone                                       5       2,6-Diaminopyridine                                                                              Lawsone                                              6       2,6-Diaminopyridine                                                                              β-Naphthoquinone                                7       2,6-Diaminopyridine                                                                              α-Naphthoquinone                               8       2,6-Diaminopyridine                                                                              α-Naphthoquinone                               9       3,6-Diaminoacridine                                                                              p-Benzoquinone                                      10       3,6-Diaminoacridine                                                                              α-Naphthoquinone                              11       1,6-Diaminoacridine                                                                              α-Naphthoquinone                              12       3,9-Diaminoacridine                                                                              p-Benzoquinone                                      13       4,9-Diamino-2-hydroxyacri-                                                                       Lawsone                                                      dine                                                                  14       4,9-Diaminoacridine-2-sul-                                                                       p-Benzoquinone                                               fonic acid                                                            15       2,4-Diamino-6-hydroxy-                                                                           α-Naphthoquinone                                       pyrimidine                                                            16       2,4-Diamino-6-hydroxy-                                                                           p-Benzoquinone                                               pyrimidine                                                            17       4,6-Diaminopyrimidine                                                                            α-Naphthoquinone                              18       2,4,5-Triaminopyrimidine                                                                         β-Naphthoquinone                               19       2,4-Diaminopyrimidine-5-                                                                         Lawsone                                                      carboxylic acid                                                       20       4,6-Diaminopyrimidine-2-                                                                         α-Naphthoquinone                                       sulfonic acid                                                         21       2,4-Diaminothiazole                                                                              α-Naphthoquinone                              22       2,4-Diaminothiazole-5-                                                                           α-Naphthoquinone                                       carboxylic acid                                                       23       2,5-Diaminobenzothiazole                                                                         p-Benzoquinone                                      24       5,8-Diaminoquinoline                                                                             p-Benzoquinone                                      25       5,8-Diaminoquinoline                                                                             p-Benzoquinone                                      26       4,8-Diaminoquinoline                                                                             α-Naphthoquinone                              ______________________________________                                    

                  TABLE 2                                                          ______________________________________                                                 Total                                                                  Condensa-                                                                              conc. of  (A):(B)        Reaction                                                                              Reaction                               tion pro-                                                                              (A) + (B) (wt.           tempera-                                                                              time                                   duct No.                                                                               (wt. %)   ratio)  Solvent                                                                               ture (°C.)                                                                     (hour)                                 ______________________________________                                          1      10          1:1.5 Methanol                                                                              65     10                                      2*     10        --      Methanol                                                                              65     10                                      3*     10        --      Methanol                                                                              65     10                                      4      10          1:0.5 Methanol                                                                              65     10                                      5      20        1:1     Ethanol                                                                               80     10                                      6      10          1:1.5 Methanol                                                                              65     20                                      7      10        1:3     Methanol                                                                              65     20                                      8       3        1:3     Methanol                                                                              65     40                                      9       2        1:1     Ethanol                                                                               65     10                                     10       2        1:2     Ethanol                                                                               65     10                                     11       2          1:1.5 Ethanol                                                                               65     10                                     12       2          1:0.5 Ethanol                                                                               65     40                                     13       1        1:1     Ethanol                                                                               80     20                                     14       2        1:1     Ethanol                                                                               65     10                                     15      10        1:1     Methanol                                                                              65     10                                     16      10        1:2     Methanol                                                                              65     10                                     17      10          1:1.5 Methanol                                                                              65     10                                     18      10          1:0.5 Methanol                                                                              65     40                                     19      20        1:1     Ethanol                                                                               80     20                                     20      10        1:1     Methanol                                                                              65     10                                     21      10          1:1.5 Methanol                                                                              65     10                                     22      10        1:3     Methanol                                                                              65     10                                     23       5          1:0.5 Ethanol                                                                               65     20                                     24      10          1:1.5 Methanol                                                                              65     10                                     25      10        1:3     Methanol                                                                              65     10                                     26       5          1:0.5 Ethanol                                                                               65     20                                     ______________________________________                                    

EXAMPLE 1 (Experiment Nos. 101 to 126)

In each experiment, a stainless-steel polymerization vessel having an internal capacity of 1000 liters and equipped with a stirrer was used to carry out polymerization.

In preparing a polymer scale preventive agent in each experiment, the condensation product (F), water-soluble polymeric compound (C), inorganic colloid (D), alkali metal silicate (E), alkaline compound and solvent set forth in Table 3 were used in such amounts as to produce the solvent composition, total concentration of (F)+(C)+(D)+(E), weight ratio of (F):(C):(D):(E), and pH shown in Table 4. The inorganic colloids (a to g, in Tables 3 and 7) which were used as component (D) in this example and Example 2 described below are shown in Table 6.

In each experiment, the polymer scale preventive agent prepared as above was applied to the inner wall of the polymerization vessel and to the stirring shaft, stirring blades and the like parts with which the monomer comes into contact during polymerization. The polymer scale preventive agent thus applied was dried by heating at 40° C. for 15 minutes to form a coating, followed by washing with water.

Subsequently, in each experiment, polymerization was conducted as follows. The polymerization vessel provided with the coating by the coating treatment as above was charged with 400 kg of water, 200 kg of vinyl chloride, 250 g of partially saponified polyvinyl alcohol, 25 g of hydroxypropyl methyl cellulose and 70 g of 3,5,5-trimethylhexanoyl peroxide, followed by polymerization with stirring at 66° C. for 6 hours. After the polymerization was finished, the polymeric product and unreacted monomer were recovered, and the inside of the polymerization vessel was washed with water to remove residual resin.

Thereafter, the above process including the polymerization and the washing of the inside of polymerization vessel with water was repeated batchwise, without carrying out the coating operation, the repetition number of batch being given in Table 5. After the final batch was over, the amount of polymer scale deposited on areas located in the liquid-phase region and that on areas around the interface between gas and liquid phases inside the polymerization vessel were determined according to the method described below. The results are given in Table 5.

Measurement of the amount of polymer scale deposited

The scale deposited in an area of 10 cm square at a predetermined location on the inner wall of a polymerization vessel is scraped off with a stainless steel spatula as completely as can be confirmed with the naked eye, and then the scraped scale is weighed on a balance. The measured value is multiplied by 100 to obtain the amount of the deposited polymer scale per area of 1 m².

Besides, the number of fish eyes appearing upon formation of a polymer into a sheet was measured with respect to the polymers obtained in the experiments, according to the method below. The results are given in Table 5.

Measurement of fish eyes

A hundred (100) parts by weight of a polymer obtained, 50 parts by weight of dioctyl phthalate (DOP), 1 part by weight of dibutyltin dilaurate, 1 part by weight of cetyl alcohol, 0.25 part by weight of titanium oxide and 0.05 part by weight of carbon black are mixed. The resulting mixture is kneaded at 150° C. for 7 minutes with 6 inch rolls, and then formed into a sheet 0.2 mm thick. The obtained sheet is examined for the number of fish eyes per 100 cm² by light transmission.

Further, measurement of luminosity index (L value) of a sheet formed from a polymer was carried out, according to the method below, with respect to the polymers produced in the experiments. The results are given in Table 5.

Measurement of luminosity index (L value)

A hundred (100) parts by weight of the obtained polymer, 1 part by weight of a tin laurate stabilizing agent (TS-101, product of Akisima Chemical Co.) and 0.5 part by weight of a cadmium stabilizing agent (C-100J, product of Katsuta Kako Co.), and 50 parts by weight of dioctyl phthalate as a plasticizer are kneaded at 160° C. for 5 minutes with a twin roll mill, and then formed into a sheet 1 mm thick. Subsequently, this sheet is placed in a mold measuring 4×4×1.5 cm, heated at 160° C. under a pressure of 65 to 70 kgf/cm² for 0.2 hour and press molded under the same conditions to prepare a test specimen. This test specimen is measured for luminosity index L in the Hunters color difference equation described in JIS Z 8730 (1980). The greater the value of L, the higher the whiteness evaluated, namely, the slighter the initial coloration evaluated.

The value of L is determined as follows.

The stimulus value Y of XYZ color system is determined by the photoelectric tristimulus colorimetry using the standard light C, photoelectric colorimeter (Color measuring color difference meter Model Z-1001DP, product of Nippon Denshoku Kogyo K.K.) in accordance with JIS Z 8722. As the geometric condition of illumination and light reception, the condition d defined in section 4.3.1 of JIS Z 8722 is adopted. From the stimulus value Y obtained, the L value is calculated based on the equation: L=10Y^(1/2) described in JIS Z 8730 (1980).

                  TABLE 3                                                          ______________________________________                                         Polymer scale preventive agent                                                      (F)        (C)                 (E)                                             Condensation                                                                              Water-soluble                                                                               (D)    Alkali                                     Exp. product    polymeric    Inorganic                                                                             metal                                      No.  No.        compound     colloid                                                                               silicate                                   ______________________________________                                         101   1         Gelatin      b      --                                          102*                                                                                2*        Gelatin      b      --                                          103*                                                                                3*        Gelatin      b      --                                         104   4         Polyacrylic acid                                                                            c      --                                         105   5         Na salt of car-                                                                             a      --                                                         boxymethyl                                                                     cellulose                                                      106   6         --           --     --                                         107   7         Polyvinyl alcohol                                                                           d      --                                         108   8         Polyvinyl    --     sodium                                                     pyrrolidone         methasilicate                              109   9         Gelatin      b      --                                         110  10         Polyacrylic acid                                                                            c      --                                         111  11         Na salt of car-                                                                             a      --                                                         boxymethyl                                                                     cellulose                                                      112  12         --           --     --                                         113  13         Polyvinyl alcohol                                                                           d      --                                         114  14         Polyvinyl    --     sodium                                                     pyrrolidone         methasilicate                              115  15         Gelatin      b      --                                         116  16         Polyacrylic acid                                                                            c      --                                         117  17         Na salt of car-                                                                             a      --                                                         boxymethyl                                                                     cellulose                                                      118  18         --           --     --                                         119  19         Polyvinyl alcohol                                                                           d      --                                         120  20         Polyvinyl    --     sodium                                                     pyrrolidone         methasilicate                              121  21         Gelatin      a      --                                         122  22         Polyvinyl    d      --                                                         pyrrolidone                                                    123  23         --           --     --                                         124  24         Gelatin      a      --                                         125  25         Polyvinyl    d      --                                                         pyrrolidone                                                    126  26         --           --     --                                         ______________________________________                                    

                                      TABLE 4                                      __________________________________________________________________________     Polymer scale preventive agent                                                    Total conc.                                                                    of (F) + (C) +  Alkaline                                                    Exp.                                                                              (D) + (E)                                                                              (F):(C):(D):(E)                                                                        compound     Solvent                                        No.                                                                               (wt. %) (weight ratio)                                                                         (pH)         (weight ratio)                                 __________________________________________________________________________     101                                                                               0.3     100:100:100:--                                                                         NaOH     (10.0)                                                                             Water:Methanol (70:30)                          102*                                                                             0.3     100:100:100:--                                                                         NaOH     (10.0)                                                                             Water:Methanol (70:30)                          103*                                                                             0.3     100:100:100:--                                                                         NaOH     (10.0)                                                                             Water:Methanol (70:30)                         104                                                                               0.3     100:50:100:--                                                                          NaOH     (10.0)                                                                             Water:Methanol (90:10)                         105                                                                               0.3     100:50:200:--                                                                          KOH      (11.0)                                                                             Water:Methanol (90:10)                         106                                                                               0.5     --      Ethylenediamine                                                                         (11.0)                                                                             Water:Methanol (90:10)                         107                                                                               0.5     100:100:200:--                                                                         NaOH     (11.0)                                                                             Water:Methanol (90:10)                         108                                                                               0.5     100:100:--:300                                                                         NaOH     (11.0)                                                                             Water:Acetone (90:10)                          109                                                                               0.3     100:100:100:--                                                                         NaOH     (10.0)                                                                             Water:Ethanol (70:30)                          110                                                                               0.3     100:50:100:--                                                                          NaOH     (10.0)                                                                             Water:Ethanol (90:10)                          111                                                                               0.3     100:50:200:--                                                                          KOH      (11.0)                                                                             Water:Ethanol (90:10)                          112                                                                               0.5     --      Ethylenediamine                                                                         (11.0)                                                                             Water:Ethanol (90:10)                          113                                                                               0.5     100:100:200:--                                                                         NaOH     (11.0)                                                                             Water:Ethanol (90:10)                          114                                                                               0.5     100:100:--:300                                                                         NaOH     (11.0)                                                                             Water:Ethanol (90:10)                          115                                                                               0.3     100:100:100:--                                                                         NaOH     (10.0)                                                                             Water:Methanol (70:30)                         116                                                                               0.3     100:50:100:--                                                                          NaOH     (10.0)                                                                             Water:Methanol (90:10)                         117                                                                               0.3     100:50:200:--                                                                          KOH      (11.0)                                                                             Water:Methanol (90:10)                         118                                                                               0.5     --      Ethylenediamine                                                                         (11.0)                                                                             Water:Methanol (90:10)                         119                                                                               0.5     100:100:200:--                                                                         NaOH     (11.0)                                                                             Water:Methanol (90:10)                         120                                                                               0.5     100:100:--:300                                                                         NaOH     (11.0)                                                                             Water:Acetone (90:10)                          121                                                                               0.5     100:100:100:--                                                                         NaOH     (11.0)                                                                             Water:Methanol (70:30)                         122                                                                               0.5     100:50:200:--                                                                          NaOH     (11.0)                                                                             Water:Methanol (80:20)                         123                                                                               0.5     --      Ethylenediamine                                                                         (11.5)                                                                             Water:Methanol (90:10)                         124                                                                               0.5     100:100:100:-                                                                          NaOH     (11.0)                                                                             Water:Methanol (70:30)                         125                                                                               0.5     100:50:200:--                                                                          NaOH     (11.0)                                                                             Water:Methanol (80:20)                         126                                                                               0.5     --      Ethylenediamine                                                                         (11.5)                                                                             Water:Methanol (90:10)                         __________________________________________________________________________

                  TABLE 5                                                          ______________________________________                                                 Results of polymerization                                              Repeti-   Polymer                                                              tion      scale amount (g/m.sup.2)                                                                        Number   Lumino-                                         number           Around interface                                                                          of     sity                                   Exp. of       Liquid  between gas                                                                               fish   index                                  No.  batch    phase   and liquid phases                                                                         eyes   (L)                                    ______________________________________                                         101  3        0       6          16     73.0                                    102*                                                                               2        18      100        39     73.0                                    103*                                                                               2        22      90         37     73.0                                   104  4        0       8          17     73.0                                   105  3        0       6          15     73.0                                   106  2        0       20         21     73.0                                   107  3        0       7          16     73.0                                   108  5        0       6          15     73.0                                   109  3        0       8          18     73.0                                   110  4        0       10         20     73.0                                   111  3        0       8          18     73.0                                   112  2        0       25         30     73.0                                   113  3        0       8          20     73.0                                   114  5        0       8          20     73.0                                   115  3        0       8          18     73.0                                   116  4        0       10         19     73.0                                   117  3        0       10         18     73.0                                   118  2        0       20         23     73.0                                   119  3        0       8          18     73.0                                   120  5        0       8          18     73.0                                   121  3        0       9          18     73.0                                   122  3        0       8          16     73.0                                   123  3        1       25         26     73.0                                   124  3        0       8          16     73.0                                   125  3        0       7          14     73.0                                   126  3        1       22         30     73.0                                   ______________________________________                                    

                  TABLE 6                                                          ______________________________________                                         Inorganic                                                                             Diameter of                                                             colloid                                                                               colloidal particles                                                                         Name of article                                                                            Manufacturer                                   ______________________________________                                         a      10˜20 mμ                                                                           Snowtex O*  Nissan Chemical                                                    (colloidal silica)                                                                         Industries, Ltd.                               b      5˜7 mμ                                                                             Snowtex     Nissan Chemical                                                    CXS-9*      Industries, Ltd.                                                   (colloidal silica)                                         c      100˜200 mμ                                                                         Titanium oxide                                                                             Nissan Chemical                                                                Industries, Ltd.                               d      10˜20 mμ                                                                           Aluminum    Nissan Chemical                                                    oxide       Industries, Ltd.                               e      60˜70 mμ                                                                           Zirconium   Nissan Chemical                                                    oxide       Industries, Ltd.                               f      20˜50 mμ                                                                           Tin oxide   Nissan Chemical                                                                Industries, Ltd.                               g      10˜15 mμ                                                                           Iron hydroxide                                                                             produced by the                                                                present inventors                              ______________________________________                                          Note                                                                           *Trade name                                                              

EXAMPLE 2 (Experiment No. 201 to 226)

In each experiment, a stainless-steel polymerization vessel having an internal capacity of 20 liters and equipped with a stirrer was used for polymerization.

In preparation of a polymer scale preventive agent in each experiment, the condensation product (F), water-soluble polymeric compound (C), inorganic colloid (D), alkali metal silicate (E), alkaline compound and solvent set forth in Table 7 were used in such amounts as to produce the solvent composition, total concentration of (F)+(C)+(D)+(E), weight ratio of (F):(C):(D):(E), and pH given in Table 8. The polymer scale preventive agent thus prepared was applied to the inner wall of the polymerization vessel and to the stirring shaft, stirring blades and the like areas with which the monomer comes into contact during polymerization. The polymer scale preventive agent applied was dried by heating at 40° C. for 15 minutes to form a coating, followed by washing the inside of the polymerization vessel with water.

Subsequently, in each experiment, polymerization was carried out as follows. The polymerization vessel provided with the coating as above was charged with 9 kg of water, 225 g of sodium dodecylbenzenesulfonate, 12 g of t-dodecyl mercaptan and 13 g of potassium peroxodisulfate. The inside atmosphere of the polymerization vessel was replaced with nitrogen gas, thereafter 1.3 kg of styrene and 3.8 kg of butadiene were charged into the vessel, and polymerization was carried out at 50° C. for 20 hours. After the polymerization was completed, the polymeric product and unreacted monomers were recovered, followed by washing the inside of the vessel with water to remove residual resin.

Thereafter, the above process including the polymerization and the washing of the inside of polymerization vessel with water was repeated batchwise, without carrying out the coating operation, the repetition number of batch being given in Table 9. After the final batch was over, the amount of polymer scale deposited on areas located in the liquid-phase region and that on areas around the interface between gas and liquid phases inside the polymerization vessel were determined according to the same method as in Example 1. The results are given in Table 9.

Besides, measurement of luminosity index (L value) of a sheet formed from a polymer was carried out with respect to each of the polymers produced in the experiments, according to the method below. The results are given in Table 9.

Measurement of luminosity index (L value)

To 1 kg of the polymer latex obtained was added 1 kg of 2% magnesium sulfate solution to cause aggregation and sedimentation. The sediment was filtered off, washed with a hot water at 80° to 90° C. twice or three times and dried at 40° C. for 25 hours in a vacuum dryer to give a resin.

The resin was placed in a mold measuring 9×9×0.1 cm (depth), heated at 195° C. under a pressure of 50 to 60 kgf/cm² for 0.2 hour and press molded under a final pressure of 80 kgf/cm² to prepare a test specimen. This test specimen was measured for luminosity index L in the same manner as in Example 1.

                  TABLE 7                                                          ______________________________________                                         Polymer scale preventive agent                                                       (F)        (C)                   (E)                                           Condensation                                                                              Water-soluble  (D)    Alkali                                  Exp.  product    polymeric      Inorganic                                                                             metal                                   No.   No.        compound       colloid                                                                               silicate                                ______________________________________                                         201    1         Polyacrylic acid                                                                              b      --                                       202*  2*        Polyacrylic acid                                                                              b      --                                       203*  3*        Polyacrylic acid                                                                              b      --                                      204    4         Sodium alginate                                                                               e      --                                      205    5         Polyvinyl pyrrolidone                                                                         f      --                                      206    6         Polyvinyl pyrrolidone                                                                         g      --                                      207    7         --             --     --                                      208    8         Gelatin        --     Water                                                                          glass                                   209    9         Polyacrylic acid                                                                              b      --                                      210   10         Sodium alginate                                                                               e      --                                      211   11         Polyvinyl pyrrolidone                                                                         f      --                                      212   12         Polyvinyl pyrrolidone                                                                         g      --                                      213   13         --             f      --                                      214   14         Gelatin        --     Water                                                                          glass                                   215   15         Polyacrylic acid                                                                              b      --                                      216   16         Sodium alginate                                                                               e      --                                      217   17         Polyvinyl pyrrolidone                                                                         f      --                                      218   18         Polyvinyl pyrrolidone                                                                         g      --                                      219   19         --             --     --                                      220   20         Gelatin        --     Water                                                                          glass                                   221   21         Polyacrylic acid                                                                              e      --                                      222   22         Pectin         b      --                                      223   23         Casein         --     Water                                                                          glass                                   224   24         Polyacrylic acid                                                                              e      --                                      225   25         Pectin         b      --                                      226   26         Casein         --     Water                                                                          glass                                   ______________________________________                                    

                                      TABLE 8                                      __________________________________________________________________________     Polymer scale preventive agent                                                    Total conc.                                                                    of (F) + (C) +  Alkaline                                                    Exp.                                                                              (D) + (E)                                                                              (F):(C):(D):(E)                                                                        compound     Solvent                                        No.                                                                               (wt. %) (weight ratio)                                                                         (pH)         (weight ratio)                                 __________________________________________________________________________     201                                                                               0.5     100:100:100:--                                                                         NaOH     (10.0)                                                                             Water:Methanol (70:30)                          202*                                                                             0.5     100:100:100:--                                                                         NaOH     (10.0)                                                                             Water:Methanol (70:30)                          203*                                                                             0.5     100:100:100:--                                                                         NaOH     (10.0)                                                                             Water:Methanol (70:30)                         204                                                                               0.5     100:100:200:--                                                                         NaOH     (10.0)                                                                             Water:Methanol (70:30)                         205                                                                               0.5     100:100:300:--                                                                         NaOH     (10.0)                                                                             Water:Methanol (70:30)                         206                                                                               0.5     100:50:100:--                                                                          KOH      (10.5)                                                                             Water:Methanol (70:30)                         207                                                                               0.5     --      Ethylenediamine                                                                         (10.5)                                                                             Water:Methanol (90:10)                         208                                                                               0.5     100:200:--:100                                                                         Ethylenediamine                                                                         (11.0)                                                                             Water:Methanol (90:10)                         209                                                                               0.5     100:100:100:--                                                                         NaOH     (10.0)                                                                             Water:Ethanol (70:30)                          210                                                                               0.5     100:100:200:--                                                                         NaOH     (10.0)                                                                             Water:Ethanol (70:30)                          211                                                                               0.5     100:100:300:--                                                                         NaOH     (10.0)                                                                             Water:Ethanol (70:30)                          212                                                                               0.5     100:50:100:--                                                                          KOH      (11.0)                                                                             Water:Ethanol (70:30)                          213                                                                               0.5     --      Ethylenediamine                                                                         (11.0)                                                                             Water:Ethanol (90:10)                          214                                                                               0.5     100:200:100:--                                                                         Ethylenediamine                                                                         (11.0)                                                                             Water:Ethanol (90:10)                          215                                                                               0.5     100:100:100:--                                                                         NaOH     (10.0)                                                                             Water:Methanol (70:30)                         216                                                                               0.5     100:100:100:--                                                                         NaOH     (10.0)                                                                             Water:Methanol (70:30)                         217                                                                               0.5     100:100:300:--                                                                         NaOH     (10.0)                                                                             Water:Methanol (70:30)                         218                                                                               0.5     100:100:100:--                                                                         KOH      (11.0)                                                                             Water:Methanol (70:30)                         219                                                                               0.5     --      Ethylenediamine                                                                         (11.0)                                                                             Water:Methanol (90:10)                         220                                                                               0.5     100:200:--:100                                                                         Ethylenediamine                                                                         (11.0)                                                                             Water:Methanol (90:10)                         221                                                                               0.5     100:100:100:--                                                                         NaOH     (12.0)                                                                             Water:Methanol (70:30)                         222                                                                               0.5     100:100:200:--                                                                         NaOH     (12.0)                                                                             Water:Methanol (70:30)                         223                                                                               0.5     100:50:--:200                                                                          Ethylenediamine                                                                         (11.5)                                                                             Water:Methanol (70:30)                         224                                                                               0.5     100:100:100:--                                                                         NaOH     (12.0)                                                                             Water:Methanol (70:30)                         225                                                                               0.5     100:100:200:--                                                                         NaOH     (12.0)                                                                             Water:Methanol (70:30)                         226                                                                               0.5     100:50:200:--                                                                          Ethylenediamine                                                                         (11.5)                                                                             Water:Methanol (70:30)                         __________________________________________________________________________

                  TABLE 9                                                          ______________________________________                                         Repeti-   Results of polymerization                                            tion      Polymer scale amount (g/m.sup.2)                                                                    Luminosity                                      Exp. number   Liquid  Around interface between                                                                      index                                     No.  of batch phase   gas and liquid phases                                                                         (L)                                       ______________________________________                                         201  2        0       5              85.0                                       202*                                                                               1        20      150            85.0                                       203*                                                                               1        26      160            85.0                                      204  2        0       4              85.0                                      205  2        0       2              85.0                                      206  2        0       5              85.0                                      207  1        0       15             85.0                                      208  2        0       4              85.0                                      209  2        0       4              85.0                                      210  2        0       3              85.0                                      211  2        0       1              85.0                                      212  2        0       3              85.0                                      213  1        0       8              85.0                                      214  2        0       3              85.0                                      215  2        0       8              85.0                                      216  2        0       8              85.0                                      217  2        0       6              85.0                                      218  2        0       6              85.0                                      219  1        0       20             85.0                                      220  2        0       8              85.0                                      221  2        0       9              85.0                                      222  2        0       7              85.0                                      223  2        0       4              85.0                                      224  2        0       8              85.0                                      225  2        0       6              85.0                                      226  2        0       3              85.0                                      ______________________________________                                    

EXAMPLE 3 (Experiment Nos. 301 to 305)

In each experiment, a stainless-steel polymerization vessel having an internal capacity of 20 liters and equipped with a stirrer was used to carry out polymerization.

In each experiment, a polymer scale preventive agent (the one used in the experiment whose number (No.) is shown in Table 10) was applied to the inner wall of the polymerization vessel and to the stirring shaft, stirring blades and the like parts with which monomers come into contact during polymerization. The agent applied was dried by heating at 50° C. for 15 minutes to form a coating, followed by washing with water.

Thereafter, in each experiment, polymerization was carried out as follows. The polymerization vessel provided with the coating as above was charged with 40 kg of water and 6 g of sodium dodecylbenzenesulfonate, and temperature was raised to 60° C. with stirring. After the gas phase in the polymerization vessel was replaced with nitrogen gas, the vessel was further charged with 94 g of n-butyl acrylate, 220 g of methyl methacrylate, 5 g of acrylic acid and 5 g of methacrylic acid. Subsequently, 1 g of ammonium persulfate and 1 g of sodium hydrosulfite were charged into the polymerization vessel, and the resulting mixture in the vessel was stirred at 60° C. for 20 minutes.

Furthermore, into the polymerization vessel were added a monomeric mixture (prepared by mixing 2.1 kg of n-butyl acrylate, 4.8 kg of methyl methacrylate, 100 g of acrylic acid and 100 g of methacrylic acid), 500 g of an aqueous 1 wt. % ammonium persulfate solution, 500 g of an aqueous 1 wt. % sodium hydrosulfite solution and 2.0 kg of an aqueous 25 wt. % polyoxyethylene nonyl phenyl ether solution, evenly over a 3-hour period. After the addition was completed, the polymerization vessel was heated to 70° C. and polymerization was carried out for 2 hours.

After the polymerization was over, the resulting polymeric product and unreacted monomers were recovered, and the inside of the vessel was washed with water to remove residual resin.

Thereafter, a batch of operations from the formation of the coating through polymerization to the washing of the inside of the polymerization vessel with water as above-described was repeated 50 times. Upon the 50th batch, the amount of polymer scale deposited on areas located in the liquid-phase region and that on areas around the interface between gas and liquid phases inside the polymerization vessel were measured in the same manner as in Example 1. The results are given in Table 10.

                  TABLE 10                                                         ______________________________________                                         Polymer    Repeti-                                                             scale      tion     Results of polymerization                                  preventive number   Polymer scale amount (g/m.sup.2)                           Exp. agent     of       Liquid                                                                               Around interface between                         No.  (Exp. No.)                                                                               batch    phase gas and liquid phases                            ______________________________________                                         301  201       50       0     30                                               302  209       50       0     35                                               303  215       50       0     42                                               304  221       50       0     30                                               305  224       50       0     30                                               ______________________________________                                    

EXAMPLE 4 (Experiment Nos. 401 to 405)

In each experiment, a stainless-steel polymerization vessel having an internal capacity of 100 liter and equipped with a stirrer was used for polymerization.

In each experiment, a polymer scale preventive agent (the one used in the experiment whose number (No.) is shown in Table 11) was applied to the inner wall of the polymerization vessel and to the stirring shaft, stirring blades and the like parts with which monomers come into contact during polymerization. The agent applied was dried by heating at 50° C. for 15 minutes to form a coating, followed by washing with water.

Subsequently, in each experiment, the polymerization vessel thus provided with the coating was charged with 40 kg of water, 500 g of disproportionated potassium rhodinate, 13 kg of polybutadiene latex (solid content: 45%), 9 kg of styrene monomer, 5 kg of acrylonitrile monomer, 40 g of t-dodecyl mercaptan and 140 g of cumene hydroperoxide. Then, with the temperature inside the polymerization vessel maintained at 47° C., 200 g of grape sugar, 2 g of ferrous sulfate and 100 g of sodium pyrophosphate were charged into the vessel, and polymerization was carried out with stirring at 65° C. for 4 hours.

After the polymerization was over, the polymeric product and unreacted monomers were recovered, and the inside of the polymerization vessel was washed with water to remove residual resin.

Thereafter, a batch of operations from the formation of the coating through polymerization to the washing of the inside of the polymerization vessel with water as above-described was repeated 80 times. Upon the 80th batch, the amount of polymer scale deposited on areas located in the liquid-phase region and that on areas around the interface between gas and liquid phases inside the polymerization vessel were measured in the same manner as in Example 1. The results are given in Table 11.

                  TABLE 11                                                         ______________________________________                                         Polymer    Repeti-                                                             scale      tion     Results of polymerization                                  preventive number   Polymer scale amount (g/m.sup.2)                           Exp. agent     of       Liquid                                                                               Around interface between                         No.  (Exp. No.)                                                                               batch    phase gas and liquid phases                            ______________________________________                                         401  204       80       0     60                                               402  210       80       0     66                                               403  216       80       0     80                                               404  222       80       0     70                                               405  225       80       0     45                                               ______________________________________                                     

What is claimed is:
 1. A process for producing a polymer of a monomer having an ethylenically unsaturated double bond, which comprises polymerizing the monomer in a polymerization vessel having a coating on its inner wall surfaces, whereby polymer scale is prevented from being deposited,wherein said coating has been formed by applying an alkaline solution containing a condensation product of (A) a heterocyclic compound having at least two amino groups, and (B) a quinone compound, followed by drying.
 2. The process of claim 1, wherein said polymerization is conducted as a suspension polymerization, emulsion polymerization, solution polymerization, bulk polymerization, or gas phase polymerization.
 3. The process of claim 1, wherein said monomer comprises at least one compound selected from the group consisting of vinyl halides; vinyl esters; acrylic acid, methacrylic acid, and their esters and salts; maleic acid, fumaric acid, and their esters and anhydrides; diene monomers; styrene; acrylonitrile; vinylidene halides; and vinyl ethers.
 4. A process for producing a polymer of a monomer having an ethylenically unsaturated double bond, which comprises polymerizing the monomer in a polymerization vessel having a coating on its inner wall surfaces, whereby polymer scale is prevented from being deposited,wherein said coating has been formed by applying an alkaline solution containing a condensation product of (A) a heterocyclic compound having at least two amino groups, having the following formula (1):

    (R.sup.1).sub.k X(NH.sub.2).sub.2                          ( 1)

wherein R¹ is --OH, --COOH, --SO₃ H, --NH₂, --Cl, --Br, --I, --SH, --NO₂, --COCH₃, --OCH₃, --N(CH₃)₂, --C₆ H₅ or an alkyl group having 1 to 3 carbon atoms, and where a plurality of R¹ groups are present, they may be the same or different from each other, k is an integer of 0 to 9, and X is a heterocyclic group with a valence of k+2; and (B) a quinone compound, followed by drying.
 5. The process of claim 4, wherein X in the formula (1) is a group derived from a compound selected from the group consisting of pyrrole, indole, isoindole, carbazole, porphyrin, oxazole, thiazole, benzothiazole, imidazole, pyrazole, triazole, thiadiazole, pyridine, pyrimidine, quinoline, acridine, phenanthridine, phenanthroline, naphthyridine, furan, benzofuran, pyran, pyrrone, benzopyrylium, cumarin and xanthone, by removal of k+2 hydrogen atoms attached to a ring of said compound.
 6. The process of claim 1, wherein the component (A) comprises at least one compound which is selected from the group consisting of pyridine compounds, acridine compounds, pyrimidine compounds, thiazole compounds and quinoline compounds and which has at least two amino groups.
 7. The process of claim 1, wherein the component (A) comprises at least one compound selected from the group consisting of 2,6-diaminopyridine, 3,6-diaminoacridine, 1,6-diaminoacridine, 3,9-diaminoacridine, 4,9-diamino-2-hydroxyacridine, 4,9-diaminoacridine-2-sulfonic acid, 2,4-diamino-6-hydroxypyrimidine, 4,6-diaminopyrimidine, 2,4,5-triaminopyrimidine, 2,4-diaminopyrimidine-5-carboxylic acid, 4,6-diaminopyrimidine-2-sulfonic acid, 2,4-diaminothiazole, 2,4-diaminothiazole-5-carboxylic acid, 5,8-diaminoquinoline and 4,8-diaminoquinoline.
 8. The process of claim 1, wherein the component (B) comprises at least one compound selected from the group consisting of:the compounds having the following formula (2): ##STR3## wherein (R²)'s may be the same or different and each are --H, --NH₂, --Cl, --Br, --OH, --NO₂, --COCH₃, --OCH₃, --N(CH₃)₂, --COOH, --SO₃ H or an alkyl group having 1 to 3 carbon atoms; the compounds having the following formula (3): ##STR4## wherein (R²)'s may be the same or different and each are as defined above; the compounds having the following formula (4): ##STR5## wherein (R²)'s may be the same or different and each are as defined above, and (R³)'s may be the same or different and each are --H, --Cl, --Br, --OH, --COCH₃, --OCH₃, --CH₃, --COOH or --SO₃ H; and the compounds having the following formula (5): ##STR6## wherein (R²)'s may be the same or different and each are as defined above, and (R³)'s may be the same or different and each are as defined above.
 9. The process of claim 1, wherein the component (B) comprises at least one compound selected from the group consisting of o- and p-benzoquinones, α-naphthoquinone, β-naphthoquinone and lawsone.
 10. The process of claim 1, wherein the condensation product comprises one which is obtained by condensing 1 part by weight of the component (A) with 0.1 to 5 parts by weight of the component (B).
 11. The process of claim 1, wherein said alkaline solution comprises water as a solvent.
 12. The process of claim 1, wherein said alkaline solution comprises a mixed solvent of water with an organic solvent miscible with water, said organic solvent being present in an amount of not more than 50% by weight based on said mixed solvent.
 13. The process of claim 1, wherein said alkaline solution has a pH of 7.5 to 13.5.
 14. The process of claim 1, wherein said coating further comprises at least one member selected from the group consisting of:(C) a water-soluble polymeric compound, (D) an inorganic colloid, and (E) an alkali metal silicate.
 15. The process of claim 1, wherein the concentration of the condensation product is 0,001 to 5% by weight.
 16. The process of claim 1 wherein said condensation product has been produced by reacting components (A) and (B) with each other at a temperature of room temperature to 200° C. for 3 to 100 hours.
 17. The process of claim 16, wherein the components (A) and (B) are reacted at a temperature of 65° C. to 200° C. for 3 to 100 hours. 